PURPOSE: To reduce the start-up time till the circuit is made stable after power- down is released with respect to the switched capacitor filter comprising an operational amplifier available of power-down operation and a switched capacitor.

CONSTITUTION: The filter is provided with a power supply used to drive the switched capacitor comprising plural switches and plural capacitors and an operational amplifier 30, and various potentials such as zero V ground level and an intermediate potential are generated, each switch is closed in the power- down mode to keep an integration capacitor 24 to be an intermediate potential, and the switches provided respectively to an input terminal and an output terminal of the filter are opened in the power-down mode.